The objective of this program is to train future leaders in environmental health sciences (EHS) by providing transdisciplinary research training that bridges environmental mechanistic toxicology and environmental molecular epidemiology with applications to human disease prevention. The program is based on the premise that modern EHS scientists specializing in toxicology or epidemiology require training in multiple disciplinary approaches in order to conduct translational research, including the evolving technologies of genomics, proteomics and bioinformatics. The proposed program is an evolution of the investigators' current program which has provided training in mechanistic toxicology for 25 years. The changes allow them to capitalize on a recent expansion in faculty conducting cutting-edge transdisciplinary research. Pre-doctoral trainees will specialize in environmental epidemiology or mechanistic toxicology, and will take a foundation course and an advanced course in the non-specialization area (i.e., epidemiology trainees take toxicology courses and visa versa). In addition, there is a common core curriculum of translational research and bioinformatics courses. To accommodate the program's expansion, the investigators request 8 pre-doctoral and 4 postdoctoral positions (at levels 0,1 and 2) in this submission, increased from 6 pre-doctoral and 2 postdoctoral positions in the last cycle. The expected duration of trainee support on this training grant is two years, though the expected total duration of pre-doctoral training is 4-5 years. Postdoctoral trainees will be encouraged to submit an F32 Individual NRSA Postdoctoral Fellowship application in their first year of training. Qualified applicants must demonstrate motivation for careers in EHS mechanistic toxicology or mechanistically-oriented epidemiology research. Pre-doctoral trainees must have a baccalaureate degree with relevant scientific coursework preparation and will be enrolled in a Ph.D. program in the Department of EHS, which has a distinguished history of graduate training in toxicology. Postdoctoral fellows must have the PhD, MD, DVM, or other appropriate doctoral degree. Although the investigators expect that most postdoctoral trainees will hold Ph.D. degrees, they also anticipate offering 1-2 postdoctoral fellowships to candidates holding clinical degrees. Relevance: This program will provide transdisciplinary training of environmental health scientists in emerging research approaches and technologies to increase the tempo of research findings that promote human disease prevention from environmental exposures.